File servers are well known in the art to designate computer equipment having some type of mass storage device, typically a magnetic hard disk, that is connected to a network and utilized as central storage for multiple users via the network. The information that is typically stored on such a system consists of binary computer data such as executable programs and corresponding data. Exemplary of the types of corresponding data stored are numbers for spreadsheets, ASCII characters and codes for word processors, and drawing commands for drawing and CAD programs. These or similar types of data do not have a time element associated with them nor do they require any extra processing beyond the usual interpretation that is accomplished by the computer program with which they are intended to be used.
In contrast, the playback of audio/video information has a time element associated with its use. Furthermore, the amount of data required to store audio/video program information in digital form is currently prohibitive. Thus, it is common to employ audio/video compression techniques to reduce the audio/video program information before it is stored. As a result, further processing in the form of decompression and digital-to-analog conversion is required before the real-time viewing of an audio/video program can take place. Decompression may be accomplished through the use of known hardware or software techniques. Digital-to-analog conversion may be required, depending on the type of equipment used for viewing the audio/video program. A known audio/video file server apparatus manufactured and marketed by Protocomm of Trevose, Pa. permits real-time playback of compressed audio/video program information. However, this prior art apparatus is disadvantageous in that it does not include any capability for less-than-real-time reception of audio/video program information for updating the audio/video program information stored therein. In addition, the hardware for accomplishing playback of stored audio/video program information is duplicated at each user station, rather than centrally located within the audio/video file server.
It is therefore the principal object of the present invention to provide a self-contained audio/video file server for receiving compressed digital audio/video program information over a time period that is less than a real time period required for viewing the audio/video program information, for centrally storing the compressed digital audio/video program information, and for selectively decompressing the stored audio/video program information and playing the selectively decompressed audio/video program information in real time to an external playback station that has requested it.
This and other objects are accomplished in accordance with the illustrated preferred embodiment of the present invention by providing a storage unit for centrally storing compressed digital audio/video program information, a transceiver for receiving compressed digital audio/video program information from an external source over a less-than-real-time period to update the stored audio/video program information, a plurality of playback units, each associated with an external playback line and an external playback station and each including a decompression unit, for receiving selected compressed digital audio/video program information from the storage unit, for decompressing the selected compressed digital audio/video program information received from the storage unit, and for playing it in real time over the associated playback line to the associated playback station, a network interface unit for receiving playback requests from the playback units, and a processor for controlling the storage and playback units to play the decompressed selected audio/video program information in real time for viewing by users at selected playback stations.